Builder Insight #1: ACQ Copper Quaternary Treated Wood online Resource Guide
Given the introduction of new types of pressure-treated wood for residential use, it is important to use the appropriate connectors, fasteners, and flashings. The phasing out of Chromated Copper Arsenate (CCA) treated lumber began on January 1, 2004 and was replaced with Alkaline Copper Quaternary (ACQ) and Copper Azole (CA) treated lumber.
The copper content in the new preservatives are significantly greater, which increases the risk of galvanic corrosion. Literature and research that is currently available from Canadian Mortgage and Housing Corporation (CMHC), manufacturers and industry organizations recommend using connectors, fasteners and flashings that are compatible with ACQ treated wood.
Materials that are compatible with ACQ pressure-treated wood include:
- Fasteners: stainless steel, hot-dipped galvanized and polymer coated.
- Connectors: stainless steel and hot-dipped galvanized. Hot-dipped galvanized connectors must have a minimum coating of G185 (more than triple the G60 coating required for CCA treated lumber).
- Flashings: stainless steel, copper and flexible membranes.
Current literature on ACQ pressure-treated wood also recommends that fasteners, connectors and flashings made of aluminum should not come into contact with ACQ treated wood including railings and door thresholds. Hot-dipped galvanized anchor bolts and G185 strap anchors should be used for ACQ foundation sill plates.
Stainless steel or hot-dipped galvanized fasteners and connectors should be used with ACQ treated wood for deck and floor ledger boards, nailing strips, interior wall sill plates (including powder actuated fastener nails), and when fastening wall sheathing to ACQ treated sill plates. The most recent information from industry and manufacturers recommend using stainless steel connectors and stainless steel fasteners for maximum service life. For more information on pressure-treated wood, visit the following sites:
Alberta New Home Warranty Program
A bulletin, Corrosion Resistant Connectors for the New Generation of Preserved Lumber (ACQ), prepared by the Alberta New Home Warranty Program includes information on corrosion resistant products that are compatible with ACQ treated wood and links to other sources of information.
Canada Mortgage and Housing Corporation
The CMHC research report Incompatible Building Materials Research has valuable information on building material incompatibilities, including treated lumber and metal fasteners.
Canadian Institute of Treated Wood
This site has links to treated wood and fastener manufacturers, and information on the use, handling, installation, maintenance and disposal of treated wood.
Canadian Wood Council
This site has information on the transition from CCA treated wood to ACQ and CA Preservative Treated Wood, the manufacturing process, retention and penetration of the preservatives, finishing and applications, and additional links.
Durable Wood
Forintek Canada and Canadian Wood Council's Durable Wood website provides information regarding preservative treated wood that is more technical in nature including performance data, codes and standards and additional links.
Using the Correct Fasteners for Treated Wood
This Solplan Review (No. 115, March 2004) article discusses the use of appropriate fasteners and connectors with ACQ and CA treated wood. This issue also contains an article on CCA treated wood. E-mail Solplan for more information.
